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 Hynautic Steering Fluid Change - Best way?

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rodell Posted - Feb 23 2007 : 18:09:08

I have a leaky Hynautic, dual-helm steering system. In the process of discovering the leak, I found the system is filled with ATF. (New boat to me this week.) This fluid is ok, but, not recommended.

Since I have to fix the system, what's the best way to clean out the old and put in new fluid? The flybridge helm is easy to get to, but the lower helm not so much.

I can't think of any good method of cleaning it out other than to fill the reservoir with new oil and pump it through until it cleans up. That could be a lot of oil, given the Teleflex steering oil is lighter weight.

Does anyone have any ideas on the best way to make this change?

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diver dave Posted - Feb 24 2007 : 19:09:12
I had ATF in my hynatic system, also with dual helms. It got changed to hydraulic fluid because my boat is plumbed with 3/8" tubing, not larger hose. That made steering slightly more difficult due to the higher viscosity of ATF. If steering effort is not a factor to you, the ATF is fine, and will give you a nice indication of leaks. It won't hurt anything. If you want to get it out, vacuum out the resevoir, replace, pump up, then open the bleeds at the cylinder one at a time. Drive the piston towards the bleed screw being used to limit the trapped atf in the cylinder. Perform the bleeding procedure, then vacuum the resevoir one more time.
New2Me34C Posted - Feb 24 2007 : 13:23:21
You may find the info you need via a link or two at this site. or this one
rodell Posted - Feb 24 2007 : 11:57:23
As I've researched this issue, I find that some shops (and people, I presume) have used a red-dyed hydraulic fluid, either from aircraft or other sources. My particular installation is from 2001, and, it is in that timeframe some technicans remember some fluids that were red that weren't ATF. This isn't very conclusive, but, is just one piece of input.

The newer fluids from Teleflex are almost clear.

I'm going to hate it, but, I'm going to have to drain it all and start over if I really want to know. I still wonder if I can empty the reservoir, fill it with new fluid, and pump it out the return line (3-line system) without disconnecting everything and trying to drain it that way.

navman Posted - Feb 24 2007 : 11:34:38
From what I have seen it is different color, but I only seen one sample of Hynautic fluid for steering , it was more of a clear fluid and expensive. ATF is more reddish.
My shift control Hynautic unit takes antifreeze. I use green.
New2Me34C Posted - Feb 24 2007 : 08:22:49
Question: How can you tell what type of fluid is in your system by looking at it? Different color?
Would you have to bleed the pressure and drain some of it to check this?

Silverton_34 Posted - Feb 23 2007 : 20:05:37
I have a 1990 and the Hynautic unit has ATF. The previous owner said that is what he used and so did the owner before him. If it really bothers you then change it otherwise use ATF.
rodell Posted - Feb 23 2007 : 18:39:31
I came to the conclusion it should be changed because of the multiple warnings about using the right fluid in the Hynautic manual, and, the statement "ATF should only be used in an emergency".

Like most things in boating, cost isn't the primary driver for me, I can't speak for the previous owner.

I have heard that some Hynautic systems used aviation hydraulic fluid that is marked with red dye - maybe I don't have ATF in it at all (the puddle is red). The previous owner left me nothing.

navman Posted - Feb 23 2007 : 18:21:06
It is probably filled with ATF because it is so much cheaper to buy, if you were not having problems with it then just stay the course, fix the leak and then bleed the air out.
I just helped my Doctor bleed his lines last week, he had a leak on his upper helm and repaired it. On the reservoir he had 2 bleed valves below the reservoir, one on top of the other. one is for turning port the other is for turning starboard.
Took us a while to figure this out cause we thought the top was for upper helm and the bottom for lower. So once you fix the leak then you can fill reservoir (make sure you releave all pressure before opening fill cap, or else) then add recommended pressure with tire pump. Then open valves and have somebody turn your wheel all the way left and right until the air bleeds out. You will feel the resistance on the wheel itself once the air is removed. Then tighten up amd make sure pressure is where it belongs, 30 psi in most steering units I have had.

May be not all systems have the bleed valves in the same place either.

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